1. Field of the Invention
The present invention relates to a print head unit and method and device for evaluation of the print head unit.
2. Description of Related Art
A conventional method for evaluation a print head unit will be described while referring to FIGS. 1 and 2. The print head unit is evaluated to determine whether or not it can eject an ink droplet properly. A print head unit 101 is used in a printing device, and includes a print head 102, a flexible substrate 130 connected to the print head 102, and a driver IC chip 103 attached on the flexible substrate 130. The driver IC chip 103 includes a driving circuit 103a for driving the print head 102 and a unit interface 103b integrally formed with the driving circuit 103a. A control signal generation circuit (not shown) provided in the printing device main body generates print control signals, such as print clock signals. Such print control signals are transmitted to the driving circuit 103a via the unit interface 103b. Some of control signals such as those including print data transmitted to the driving circuit 103a are further transmitted to the print head 102 via the flexible substrate 130. The print head 102 is formed with an actuator 102a, an ink supply channel 102b, and a nozzle 112a. Ink K stored in an ink cartridge (not shown) is supplied to the actuator 102a through the ink supply channel 102b, and ejected as ink droplets from the nozzle 112a. In order to evaluate quality of the print head unit 101 a testing terminal 131 is provided between the print head 102 and the driving circuit 103a on the flexible substrate 130. The testing terminal 131 detects a waveform of a voltage outputted from the driving circuit 103a to the print head 102. When the quality of the print head unit 101 is satisfactory, the voltage has a normal waveform.
However, because the above-described print head unit 101 has the driving circuit 103a on the flexible substrate 130, its manufacturing costs are relatively high. In order to overcome this problem, there has been proposed a chip-on-head type print head unit, in which a driving circuit is provided directly on a print head without a flexible substrate therebetween. The print head and the driving circuit are connected to each other via signal lines. Manufacturing costs of this chip-on-head type of print head unit are lower than the conventional one. However, the signal lines are so delicate that a testing terminal cannot be provided on the signal lines. That is, the above-described evaluating method cannot be applied to the chip-on-head type of print head unit. As a result, in order to evaluate quality of this type of print head unit, a user needs to mount the print head unit into a printing device and perform a printing operation to print an image on a print medium. Then, the user examines the printed image and determine the quality of the print head unit.